CODEWITHSUNDEEP
imageoverlaygoogle-earth
Jeff Storey
Jeff Storey

Reputation: 57192

How can I use an image to overlay the entire earth in Google Earth?

I'm trying to overlay a map around the entire earth in Google Earth. Is there a certain dimension the image needs to be for this?

Upvotes: 0

Views: 2261

Answers (2)

user354134
user354134

Reputation:

Actually, setting west to -180 and east to 180 doesn't quite work, but -179.99 and 179.99 do work. Other issues:

  • I created a 1024x512 transparent image with only one pixel (256,128) "lit". As you can see at http://test.barrycarter.info/gmap17.php, the lit pixel (near Wausau, WI, USA) is about the size of the nearby twin cities of Minneapolis and St Paul.

  • If you zoom in after a certain point, the pixel mysteriously vanishes.

  • GroundOverlays are clickable (I can't find a way to turn this off), so if you click on the map to zoom, you get an annoying popup. Using the scale works fine.

  • I also created a 2048x1024 transparent image with one pixel lit at http://test.barrycarter.info/gmap18.php but even that pixel is too big. Higher resolutions are also noticeably slower to load.

On the other hand, placing too many groundoverlays makes the map rendering painfully slow. Google presumably renders KML maps itself, but I think the groundoverlays are still "img src"'d in.

The holy grail here is to find the right combination of resolution and number of images: eg, 64 images each covering 1/64th of the Earth.

EDIT: Since google maps shows the whole world at level 2, and zooms as far as level 20, you ultimately need 2^18==262144 pixels in each direction, provided your pixel was the size of the entire map at a lavel 20 zoom. That's 4096 images of 4096x4096 each or 68.7 gigapixels. Of course, if you don't need level 20 zooming, you can cut that down a lot.

Upvotes: 0

Bryan
Bryan

Reputation: 1893

You can generate images in Google Earth by making a KML file. In a KML file there is a GroundOverlay tag that you can use to accomplish your goal like this:

<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://www.opengis.net/kml/2.2">
  <Folder>
    <name>Ground Overlays</name>
    <description>Examples of ground overlays</description>
    <GroundOverlay>
      <name>Large-scale overlay on terrain</name>
      <description>Overlay shows Mount Etna erupting 
          on July 13th, 2001.</description>
      <Icon>
        <href>http://code.google.com/apis/kml/documentation/etna.jpg</href>
      </Icon>
      <LatLonBox>
        <north>37.91904192681665</north>
        <south>37.46543388598137</south>
        <east>15.35832653742206</east>
        <west>14.60128369746704</west>
        <rotation>-0.1556640799496235</rotation>
      </LatLonBox>
    </GroundOverlay>
  </Folder>
</kml>

Here are a few links to help you understand kml files and image overlays:

KML Tutorial
KML Tutorial - Ground Overlays
Image Overlay Creator for Google Earth - Google Earth Blog

Upvotes: 4

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